Sleep disturbances are common during pregnancy. Over a quarter of pregnant women develop sleep- disordered breathing. Many pregnant women experience poor sleep quality and continuity. Growing evidence from studies of the general population shows that sleep-disordered breathing, short sleep duration and poor sleep quality (including reduced slow wave sleep) are independently associated with increased risk of metabolic syndrome, type 2 diabetes and insulin resistance. Preliminary studies in pregnancy have found a similar, analogous relationship between these problems (self-reported sleep-disordered breathing and short sleep duration) and gestational diabetes mellitus (GDM). We have also found that a moderate/severe sleep apnea and daytime napping are both associated with hyperglycemia during pregnancy. Thus, sleep disturbances may constitute a class of novel MODIFIABLE risk factors for GDM. GDM is associated with adverse maternal-fetal outcomes and is also a predictor of type 2 diabetes, cardiovascular disease and obesity in both mother and child. The aims of the proposed study are (1) to evaluate changes in slow wave sleep during pregnancy as well as obtain advanced training (K99 phase) and (2) to investigate the independent association of sleep disturbances and characteristics with gestational diabetes in a case-control study (R00 phase). In the K99 mentored phase, slow wave sleep changes will be determined using archival polysomnography data gathered from pregnant women in their first and third trimesters. During this time, training in actigraphic evaluation of sleep duration and assessment of biomarkers will build upon my prior experience with electroencephalography (EEG) analysis and assessment of behavioral and subjective properties of sleep. In the R00 phase, a case-control study will be conducted to determine the independent association of sleep disturbances and sleep characteristics with GDM, recruiting 140 cases and 280 controls (1:2 match for age, race, parity and body mass index (BMI)) from the obstetrics services at the Hospital of the University of Pennsylvania (HUP) and at the Pennsylvania Hospital (PAH). Data will be collected from home-based polysomnography, sleep diary, wrist actigraphy and questionnaires. For the exploratory aim, serum samples before and after sleep will be collected. A technician blinded to case status and BMI will perform all sleep scoring.